- It's easy to get up and running if you want a basic store
- It has the best bulk product import feature I've ever seen (and I worked with dozens of ecommerce software)
- Fast load times
- You don't have to worry about security, updates etc.
- It has built-in blogging software (though very basic and limited)
- It doesn't support drop down menus out of the box and workaround that they provide often doesn't work without custom coding
- Cost - Their pricing plans are a bit misleading. I will never forget my disappointment when I encountered for the first time that they count every variant as a product. So, you have 1 product in 10 sizes and 10 colors - you already need more than a basic plan which offers 100 "products".
- They charge transaction fees
- You are limited to 3 options per product and 100 variants per product
- No FTP access
These are just some random thoughts, since you didn't specify what things are important to you or what type of store are you going to build.
Overall, I like Shopify and would recommend it. It certainly isn't for everyone and you have to give up on some flexibility, but in return you get decent all-in-one platform to work with.